1. Field of the Invention
The present invention relates to a dyeing process for polyester fibers and, more particularly, to a low temperature microemulsion dyeing process which eliminates the need for a reducing agent in a subsequent washing step.
2. Description of Related Art
The primary goals of polyester fiber dyeing processes are the attainment of deep color and high color fastness, especially for Denil and super slender fiber fabrics.
Dyeing of polyester fibers is generally accomplished by dispersing swelling agents and dyestuffs amongst the fibers in a high temperature and high pressure environment. At temperatures above 85 degree C., which is the second transfer point of the polyester fiber, the motions of the fibers and the dyestuff molecules increase so that the dyestuff molecules are easy to diffuse among the fibers, thereby improving the dyeing process. Common practice is to employ such a dyeing process at a temperature of 130 degree C. Moreover, in such a dyeing process, organic solvents selected to swell the polyester fibers for dyeing may contain phenyl-phenol, phenyl-chloride,, phenyl-alkyl group, etc. Known high temperature and high pressure dyeing processes which employ swelling agents, however, often wash the dyed fibers with sodium hydrosulfite (as known as sodium Dithionite Na.sub.2 SO.sub.2 O.sub.4) which may harm operators, residents, and the environment. A dyeing process which improves the environment of the dyeing plant, saves energy by decreasing the dyeing temperature and eliminates the need for sodium hydrosulfite is desired.